1. Field of the Invention
The present invention relates to modular concrete building forms. More specifically, the invention relates to a method and apparatus for fastening a sheet of gypsum wallboard or the like to a modular concrete building form.
2. Related Art
The use of synthetic plastic modular building block forms to construct concrete walls is becoming increasingly popular, not just in the United States, but in many European countries as well. Typically, a pair of parallel, spaced-apart side panels, formed from a material such as expanded polystyrene (EPS), are held together by a plurality of struts or ties, and are provided with interlocking upper and lower surfaces to permit stacking. The cavity between the side panels receives poured concrete, to form a building wall assembly. U.S. Pat. No. 4,730,422 to Young and U.S. Pat. No. 4,884,382 to Horobin are illustrative of this type of building wall assembly, and are incorporated herein by reference in their entireties.
Although the EPS side panel and concrete building wall assembly is simple and convenient to erect, it is not in and of itself a complete wall structure. Many, if not all, building codes require that such wall assemblies be separated from habitable space by a thermal barrier, generally a 15 minute thermal barrier. This requirement is satisfied by installation of 1/2 inch thick gypsum wallboard, provided that the attachment method also satisfies the required 15 minute thermal index.
Section 3.1.2 of the ICBO-Evaluation Service, Inc. "Acceptance Criteria for Foam Plastic Insulation," dated April 1992, stipulates that 1/2 inch gypsum wallboard installed in conformance with table 47-G of the Uniform Building Code is a complying thermal barrier. This attachment schedule requires that the gypsum wallboard be secured by drywall screws on a 16 inch O.C.E.W. pattern requiring 28 screws per 4 foot by 8 foot sheet of drywall. Alternate attachment methods can be employed when tested in compliance with UBC Standard 17-5 (Section 5.2.1 of the above-mentioned "Acceptance Criteria").
Simply securing the wallboard to the EPS side panel is insufficient, as at the temperature levels encountered in a fire, the EPS side panel will melt, and the wallboard will fall away from the concrete interior. Young proposes a method for securing furring strips to the EPS panel (illustrated in FIG. 9) by driving the wood screws into the T-shaped ends of the ties which are embedded in the EPS panel. However, because the T-shaped ends of the ties are embedded within the EPS panel, I-shaped markers (illustrated in FIG. 6), must be provided on the exterior of the EPS panel to permit the builder to locate the T-shaped ends. This method is inconvenient to execute, because once the furring strips are in place over the I-shaped indicia, the I-shaped indicia are hidden, so as to make placement of the wood screws a matter either of guess-work or repeated measurement.
It is the solution to this and other problems to which the present invention is directed.